286 ALASKAN GLACIER STUDIES but only of the tidewater ice tongues. The same is true of the explorations of Apple-gate in 1887. Davidson has summarized many of these early explorations. The explorations by United States army officers have supplied a little more information about the glaciers, because these parties were engaged in making maps. Therefore the expeditions by Abercrombie hi 1884, by Allen in 1885, by Schwatka accompanied by the geologist Hayes in 1891, by Glenn, assisted by Castner, in 1898, by Abercrombie in 1898 and 1899 have furnished maps, locations, photographs, etc., of the Miles, Childs, Valdez, Yale, Portage, and other glaciers. The utilization of the Valdez Glacier as a highway by thousands of prospectors in 1898, 1899, and 1900 added little to our knowledge of this glacier, although many mea must have taken photographs and made observations which are not now available. Then and in the years since, geologists like Hayes, Schrader, Rohn, Mendenhall,, Spencer, Moffit, and others were visiting these regions, accompanied by army officers-like Lowe and Babcock and the topographers Mahlo, Witherspoon, Gerdine, and others; and the maps, photographs, and observations by these men haye been of great service in our glacier studies. In 1899 the Harriman Expedition came to the Prince William Sound region to study the glaciers specifically and Gilbert's three days study and mapping of Columbia Glacier are of the utmost importance. He also made observations in College Fiord and Harriman Fiord, where Gannett made excellent maps and Merriam and others took glacier photographs of great value. Two observers living within this area have studied the glaciers out of interest in their behavior, and Camicia of Valdez deserves great praise for his measurements of the retreat of Valdez Glacier between 1898 and 1911, as does Johnson of the Copper River railway for his studies of Childs and Miles Glaciers in 1908 and succeeding years. The same is true of the studies of the Prince William Sound glaciers during parts of the summers of 1905, 1908, 1909, and 1910 by Grant, hi connection with his TJ. S. Geological Survey work. During part of the time he was assisted by Higgins, some of whose glacier maps are reproduced in this volume. Grant and Higgins have written an account of the glaciers and glaciation of Prince William Sound. This had not been published at the time of completing this manuscript, although after doing our own field work in 1904, 1909,1910, and 1911 we have seen the magazine articles containing abstracts of portions of their work. Grant generously allowed us to use his manuscript maps and unpublished photographs in the field, rendering our own field work much more effective. The account here presented is based upon the earlier work, especially that published by Gilbert and the Harriman Expedition, by Grant and Higgins, and by Davidson, in addition to our own field work. This field work included (1) brief observations of Valdez Glacier by the junior author in June and September, 1904, (2) a few days' study by both authors of this book in August, 1909, (3) a little over two months detailed study and mapping by the junior author between June and September, 1910, and (4) a few days' observations in June, 1911. Fifty-three of the glaciers of Prince William Sound will be discussed first, after which attention will be given to seventeen of the glaciers of the lower Copper River and to the phenomena of general glaciation in connection with these seventy larger ice tongues and certain smaller ones.